Chemical reactions: signs of a new substance, and counting atoms
Grade 8 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
A teacher mixes 4.2 g of baking soda with 100 g of vinegar in a bottle under a balloon. The liquid then weighs 102 g. What mass of gas is in the balloon, Ari?
A teacher mixes 8.4 g of baking soda with 150 g of vinegar in a bottle under a balloon. The liquid then weighs 154 g. What mass of gas is in the balloon, Bo?
A teacher mixes 2.1 g of baking soda with 50 g of vinegar in a bottle under a balloon. The liquid then weighs 51 g. What mass of gas is in the balloon, Esme?
___ Fe + 3 O₂ → 2 Fe₂O₃. Which number belongs in the blank, Jun?
- 3
- 4
- 2
- Change Fe₂O₃ to Fe₃O₃ instead
___ H₂O₂ → 2 H₂O + O₂. Which number belongs in the blank, Kira?
- 2
- Change O₂ to O instead
- 1
- 3
Milo says the fizzing cup lost mass because atoms were destroyed. Agree or disagree?
- Agree: the gas atoms vanished
- Disagree: the gas carried atoms into the air
- Agree: fizzing is just melting
- Agree: balancing changes the formulas
Noah says any bubbles prove a chemical reaction. Agree or disagree?
- Agree: bubbles mean atoms were made
- Disagree: boiling water bubbles too
- Agree: bubbles are a sure sign
- Agree: bubbles mean the water got hotter
Pia says the quickest way to balance an equation is to change the small numbers. Agree or disagree?
- Disagree: that would make a new substance
- Agree: atoms can be added to fix it
- Agree: subscripts are fine to change
- Agree: melting counts as a reaction too
Which baking soda and vinegar equation is balanced, Ren?
- NaHCO₃ + CH₃COOH → NaCH₃COO + H₂O + CO₂
- NaHCO₃ + CH₃COOH → NaCH₃COO + 2 H₂O + CO₂
- NaHCO₃ + CH₃COOH → NaCH₃COO + H₂O
- 2 NaHCO₃ + CH₃COOH → NaCH₃COO + H₂O + CO₂
Which hydrogen peroxide equation is balanced, Zee?
- 2 H₂O₂ → 2 H₂O + O₂
- H₂O₂ → H₂O + O₂
- 2 H₂O₂ → 2 H₂O + 2 O₂
- 2 H₂O₂ → H₂O + O₂